Terminalia bellirica fruit shell extract by microwave assisted extraction as a green inhibitor for mild steel acid corrosion: insight from chemical, electrochemical and computational studies

In the current study, the corrosion protection role of ethanol extract of Terminalia bellirica fruit shell on Mild Steel (MS) in 0.5 M HCl solution was studied by using weight loss, Tafel plot, AC impedance and surface techniques. The existence of functional groups in the plant extract was confirmed with the aid of FT-IR spectroscopy technique. The presence of 31.12% of gallic acid in the Terminalia bellirica fruit shell extract was complemented with HPLC and LCMS results. The surface coverage and protection efficiency of Terminalia bellirica fruit shell extract were enhanced with its concentration and declined with solution temperature. The activation parameters such as activation enthalpy, entropy and change in Gibb’s free energy are related to adsorption process were calculated and discussed. The adsorption of Terminalia bellirica fruit shell extract was found to obey the Langmuir adsorption model. The process of adsorption of inhibitor molecules on the metal surface can be verified by using UV–Visible spectroscopy technique. The potentiodynamic polarization and impedance results suggest that, Terminalia bellirica fruit shell extract functioned by adsorption at metal (MS)-Corrodent (0.5 M HCl) interface, which blocks the both cathodic and anodic half reactions of the MS corrosion process. Theoretical approach by Monte Carlo (MC) simulations and quantum chemical study support the experimental findings and adsorption of extract of Terminalia bellirica fruit shell molecules on MS surface.